In general, nitride semiconductors are in the limelight as a material for blue light emitting diodes, blue laser diodes or the like.
FIG. 1 is a sectional view of a general nitride semiconductor light emitting device.
Referring to FIG. 1, the general nitride semiconductor light emitting device includes a sapphire substrate 110, a buffer layer 120 formed on the sapphire substrate 110, an n-type nitride semiconductor layer 130 formed on the buffer layer 120, an active layer 140 formed on the n-type nitride semiconductor layer 130, and a p-type nitride semiconductor layer 150 formed on the active layer 140.
The n- and p-type nitride semiconductor layers 130 and 150 are formed by doping a variety of dopants into a gallium nitride (GaN). Representative example of n-type dopants includes silicon (Si), and representative example of p-type dopants includes magnesium (Mg).
The active layer is a layer through which light emits. As a representative growth method of the active layer, and is generally made in an InXGa1−XN (0≦x≦1) single well structure or multi-well structure in which Indium (In) and gallium (Ga) are contained in predetermined ratios. The active layer of InXGa1−XN (0≦x≦1) is generally grown under an environment of nitrogen atmosphere and at a temperature of less than 900° C.
In detail, a general growth method below 900° C. is performed in a nitrogen (N2) atmosphere for a proper composition ratio of In and Ga. However, in the thin film growth of InXGa1−XN (0≦x≦1), as the In introduction amount into GaN increases or the Ga introduction amount into InN increases, a serious phase dissociation phenomenon occurs, which is problematic. To solve such a phase dissociation phenomenon, if the growth temperature is increased, In phase dissociation phenomenon increases, which makes it difficult to obtain a good quality thin layer.
Meanwhile, when the active layer is grown in a relatively low temperature, In segregation occurs from thin InGaN layer, which deteriorates the layer quality, and many crystal defects also occur at an interface between InXGa1−XN (0≦x≦1) and GaN due to a lattice difference therebetween. Also, the In phase dissociation phenomenon increases, which makes it difficult to obtain a good quality layer, and also the occurring crystal defects are combined with crystal defects of a lower structure to decrease the light emitting efficiency and the device reliability.
Finally, in the related alt growth method, in the case of the materials, such as InGaN/GaN, a strong piezo electric field is generated inside the active layer because of a stress due to a large lattice mismatch, and electron-hole wave functions are separated, resulting in a deterioration in the light emitting efficiency.